This invention relates to fluid handling devices, such as fluid filters and lubricators, of the kind comprising a dependent liquid container. In a filter this container will serve as a collecting bowl in which the liquid separated from a throughflow is deposited to be drained off, as the separation of liquid from a pressure air supply. In a lubricator the container will provide a reservoir of liquid lubricant to be taken up by a pressure gas throughflow.
Although it is obviously desirable to make such containers from a transparent material so that the level of liquid can be readily seen, the use of glass is often unacceptable because of its brittleness. In recent years plastics materials, in particular polycarbonates have been used as a substitute, but it is found that these materials are prone to attack by impurities that may be found in industrial pressure air supplies. There are known composite constructions that avoid these disadvantages by providing a tubular sight glass mounted on a mainly metal construction, but these are relatively complex to produce and assemble, with consequently high costs, and generally require a number of separate seals giving an increased risk of leakage under pressure. There are also flat-pane sight glasses known, but these are also relatively complex to produce and assemble. Because the glass must be secured detachably if it is to be replaced without difficulty should it become broken, there is the risk of leakage past its sealing means as it will generally be secured by screws at spaced intervals around its periphery.
According to the present invention, there is provided a fluid container provided with a sight glass for indicating the fluid level therein, said sight glass being provided by an elongate light-transmitting member tapered along its length and slidable into and sealingly fitting a tapered receiving opening formed as a slot or recess in a side of the container.
In such an arrangement a sealing ring may be interposed between the sight glass and the adjoining surface of the container to encompass a wall area of the container containing at least one communicating opening in said wall to the container interior at regions adjacent both the top and the bottom of said sight glass member.
Preferably the sight glass member is insertable in said slot or recess from the top and means are arranged to be disposed above said member to limit or prevent upwards displacement of the member.
Assembly is facilitated if the sight glass member and said slot or recess are tapered both in their width and their depth transverse to the main dimension of the elongate sight glass member, i.e. transversely to the direction of insertion.
Stop means may be provided at one end of the slot or recess to limit the insertion of the sight glass member therein, and this can be conveniently achieved with a slot or recess comprising a U-form flange, the bottom of which provides said stop means.